Because of their similarities in plot and theme, all of Porter's novels are related. On the basis of subject matter, they may be divided into four groups: novels about the woods: The Song of the Cardinal (1903), Freckles (1904), A Girl of the Limberlost (1909), The Harvester (1911); novels about rural Indiana: At the Foot of the Rainbow (1907), Laddie (1913), A Daughter of the Land (1918); novels about the city: Michael O'Halloran (1915), The White Flag (1923), and novels about California: Her Father's Daughter (1921), The Keeper of the Bees (1925).